The present invention relates to an endoscopic light source apparatus for supplying illuminating light to an endoscope.
Endoscopic light source apparatus are generally of such a type that rays of illuminating light emitted from a light source, such as a built-in lamp are allowed to converge with a condenser lens and the illuminating light entrance end face of an endoscope's lightguide connector is connected near the position of their convergence.
Such endoscopic light source apparatus are useful in combination with various types of endoscopes to constitute an endoscopic system. That is, various types or kinds of endoscopes are preliminarily prepared depending on various intended uses, and selectively connected for use with a single unit of light source apparatus. To this end, the lightguide connector to be connected to the light source apparatus has the same shape and size in spite of the use of different models of endoscope. Therefore, any one of endoscopes belonging to an endoscopic system can be connected to a light source apparatus belonging to the same endoscopic system.
If the endoscopic system itself is renewed for various reasons such as making substantial modification, it is often necessary to change the size and shape of the joint between the endoscope's lightguide connector and the light source apparatus.
In renewal of the endoscopic system, there is no big problem with the light source apparatus since only one unit need be replaced. However, substituting an entirely new set of endoscopes often means an excessive economic burden on the user. To deal with this problem, the light source apparatus in a new system is generally adapted to be of such a compatible type that not only the endoscopes for the new system but also those for the old system can be connected.
In this connection, the endoscope belonging to the old system generally has a relatively long insertion section on the lightguide as a support to the light source apparatus in order to secure the positional accuracy of the illuminating light entrance end face of the endoscope's lightguide connector relative to the convergence position of the rays of illuminating light emitted from the light source lamp. In contrast, the endoscope belonging to the new system does not require such long insertion section on the lightguide since the positional accuracy can be secured by other means or mechanisms, and therefore the design trend is making the insertion section of the lightguide shorter from the viewpoint of space-saving.
However, some types of the endoscopes belonging to the new endoscopic system require the light source apparatus belonging to the new endoscopic system to have a light attenuating filter in the form of a metal screen between a lamp, i.e. the light source, and the illuminating light entrance end face of a lightguide connector in order to ensure that heat rays included in the illuminating light radiated from the lamp will not raise the temperature of the lightguide connector portion to an unduly high level that may cause a burn to the operator. An endoscope that has a relatively long insertion section on a lightguide similarly to the endoscope belonging to the old endoscopic system (and thus a distance between the light source lamp and the illuminating light entrance end face of the lightguide connector is inevitably short), an endoscope that uses a thermally weak material, such as plastic fiber (which is advantageous in view of cost reduction and which would be put into practice near future), as the lightguide, etc. are included in those types of the endoscopes.
A problem with a light source apparatus of this design is that if it is connected to an endoscope in a system that does not have to use such a light attenuating filter, the efficiency of illumination is insufficient to produce an adequate brightness of illuminating light whereas if the combination is reversed, the temperature of the lightguide connector portion is raised to an unduly high level that may potentially cause a burn to the operator.